Method For Adjusting Concrete Rheology Based Upon Nominal Dose-Response Profile

ABSTRACT

The invention relates to a method for adjusting concrete rheology requiring only that load size and target rheology value be selected initially rather than requiring inputs into and consultation of a lookup table of parameters such as water and hydration levels, mix components, temperature, humidity, aggregate components, and others. Dosage of particular rheology-modifying agent or combination of rheology-modifying agents is calculated based on a percentage of a nominal dose calculated with reference to a nominal dose response (“NDR”) curve or profile. The NDR profile is based on a correlation between a rheology value (e.g., slump, slump flow, yield stress) and the rheology-modifying agent(s) dose required to change rheology value by one unit (e.g., slump change from 2 to 3 inches) such that exemplary methods can employ corrective dosing based on the NDR and the measured deviation by the system.

FIELD OF THE INVENTION

The present invention relates to manufacturing of concrete, and moreparticularly to a method for adjusting a rheological property ofconcrete in a ready-mix truck or stationary mixer through incrementaldoses of a rheology-modifying agent calculated with reference to anominal dosage response profile.

BACKGROUND OF THE INVENTION

It is known to control the “slump” or fluidity property of concrete inready-mix delivery trucks by using sensors to monitor the energyrequired for rotating the mixing drum, such as by monitoring the torqueapplied to the drum by measuring hydraulic pressure (see e.g., U.S. Pat.Nos. 4,008,093, 5,713,663).

A hydraulic sensor coupled to the hydraulic drive and/or a rotationalspeed sensor, for example, may be used for monitoring mixing drumrotation. The monitoring of concrete slump involves calibrating theoutputs or values obtained from the hydraulic sensor and/or electricalsensor on a mixing truck containing a concrete mix and correlating thesewith slump values obtained using a standard slump cone test. In thestandard slump cone test, a 12-inch truncated cone containing the freshconcrete is removed to permit the concrete to drop, and the verticalheight drop of the concrete is measured (e.g. ASTM C143-05). Concretehaving this known slump value is added into the drum mixer so that ahydraulic or electrical value, which is obtained as an output from thesensor, can be stored into a memory location and subsequently correlatedby computer processing unit (CPU).

During the delivery of the concrete to a customer, the concrete stiffenswith time as a result of hydration, evaporation, and other factors, andthe sensors detect this as increased hydraulic or electrical energyrequired for turning the mixing drum. The on-board CPU compares thedetected energy value obtained from the sensor or sensors and comparesthis to values stored in memory. If the sensors and CPU detect that theconcrete is beginning to stiffen, the theory is that the CPU can betriggered to activate metering or pumping devices to inject water orother liquid (e.g., chemical dispersant) into the concrete to restorethe slump to the desired value.

It has long been desired to obtain the capability to add water orchemical admixture to the concrete in an efficient way, or, in otherwords, to add the precise quantity of admixture needed to achieve thetarget rheology value while avoiding dosing errors and lengthy trial anderror. The presumption has been that because highly sophisticatedsensors and CPU can be used, then an accurate and efficient methodologywould inevitably result. However, prior art cement mixing systems, forall of their evolving sophisticated hardware, remain subject tovariation in the mixture which they control.

U.S. Pat. No. 5,713,663 of Zandberg et al. declared that slump readingscould be monitored in ready-mix trucks by inputting information to anin-line CPU and that such information could include the batch wateramount, the amount of particulate material ingredients, sand moisturecontent, time, “nominated” slump, and other factors (See col. 8, lines3-14). It was not specifically explained by Zandberg et al., however,which of these factors were to be included or how they were to beweighted. The patent stated that such information could be stored intomemory such that the CPU could calculate from the inputted informationthe required liquid component needed to arrive at a desired slump. Itwas alternatively explained that the required liquid component could be“pre-calculated” and loaded into the CPU with the other information(Col. 8, lines 15-22). The patent further mentioned that the memory mayhave stored information “in a look-up table” related to “a range ofpossible mixes” and thus “for particular mix types and particular slumpvalues and particular amounts of mix ingredients, the system will beable to compare measured values by the sensors against known values forthe mix to provide for an adjustment either manually or automatically ofthe liquid component which is added” (Col. 8, lines 29-36).

Despite reiterating that the objective was to enable “maximization ofmixing without an over-supply of liquid component” which otherwiserequired the concrete mix to be returned rather than delivered, Zandberget al. did not specify what factors were to be included in the “look-up”table. Nor did they set forth the precise methodology for calculatingthe dose of the liquid component to be administered.

Similarly, U.S. Pat. Nos. 6,042,258 and 6,042,259 of Hines et al. (MBTHolding/BASF) disclosed an admixture dispensing system for stabilizingthe concrete either overnight, same day (as delivery), or for long hauloperations. In each of these modes, admixture doses were to becalculated based on “internal charts” located within computer-accessiblememory (See e.g., U.S. Pat. No. 6,042,258 at Col. 9, lines 4-30; at Col.9, lines 42-52; at Col. 10, lines 7-20; and also FIG. 2A at 128, 138,and 148). However, the number of “variables” or conditions required forinclusion on such internal charts or tables appeared to be ratherextensive. These variables included the amount of concrete in the mixer,its temperature, the type of cement in the concrete, the amount of timethat the concrete is to be in transit in the delivery truck), the amountof water required, and other factors. It was suggested that a batchmanor driver may generate his own specific charts or look-up tablesdepending on the data chosen for entry into the computer, and that thesoftware provider could make adjustments allowing for the driver orbatchman “to compensate dosage values for factors not considered in thedata charts or look-up tables” (See e.g., U.S. Pat. No. 6,042,258 atcol. 9-10; See also U.S. Pat. No. 6,042,259 at col. 9-10). Furthermore,it should be emphasized that the intent of adding admixture was tocontrol cement hydration, rather than slump or other rheology value.

In US Patent Publication 2009/0037026, Sostaric et al. (RS SolutionsLLC) disclosed a system for adjusting concrete in ready-mix deliveryvehicles using water or chemical additives. This system included sensorsfor detecting various parameters: such as temperature, pressure,rotation (speed, energy), and tilt/acceleration for calculating slump(See e.g., FIG. 4C; Para. 0071-0072). For example, the system couldinclude sensors for measuring load temperature as well as skintemperature of the mixing drum. The system could also include sensorsfor measuring “acceleration/deceleration/tilt.” The system could eveninclude sensors for measuring vibration and environmental parameters,such as humidity and barometric pressure. (See paragraph 0132).Moreover, the system would automatically add water or other admixturesbased upon the measured output of the sensors used by the system.

Despite increased technological sophistication for measuring theever-increasing number of parameters, as suggested by the increasingnumber of sensors being deployed for measuring various aspects of thecement during its delivery to a construction site, the present inventorsdo not believe that the current state of the prior art provides clearguidance about which parameters must be considered and included inlookup tables or which parameters are most important for calculatingchemical admixture dosing amounts.

Achieving accurate and efficient dosing of chemical admixtures intoconcrete is presumed to be difficult in large part due to the fact thatthe effect of added chemical admixtures on rheology is altered to agreater extent than that of water on rheology by the proportions (e.g.water to cement ratio), characteristics (e.g. cement fineness), andcondition (e.g. temperature) of the concrete ingredients and history ofthe load (age, temperature profile, etc.). These factors are likely tochange over the course of different loads of concrete batched over thecourse of a day, week, month, etc. For instance, the concretetemperature may increase with each batch during the day as the ambienttemperature increases. Different deliveries of cement may vary inchemistry and fineness.

Rather than just adjusting slump, it is desired to adjust otherrheological properties of the concrete. Rheology deals with the scienceof the flow and deformation of matter. The rheology of concrete can bedefined in terms of slump, slump flow, yield stress, plastic viscosity,apparent viscosity, thixotropy, or flow table test, among other factors.Therefore it is an object of this invent to select the proper dose ofchemical admixture to adjust one or more of such concrete rheologyparameters.

In view of the foregoing, the present inventors believe that a novelmethod for adjusting concrete rheological properties in mixing drums andother mixing devices is needed, a method that is more efficient andpractical to use than ones in current practice.

SUMMARY OF THE INVENTION

In surmounting the disadvantages and increasing technical complexity ofprior art approaches to the problem of achieving dosing accuracy andavoiding overdosing in concrete mixes, the present invention provides amethod wherein the dosing of a particular rheology-modifying agent orcombination of rheology-modifying agents is calculated using a nominaldosage response (“NDR”) profile, one that surprisingly does not requiretime-consuming compilations into a lookup table of parameters and hencethe inputting of numerous parameters at the outset of each batchpreparation or delivery.

A dose response curve relates the dose of a rheology-modifying agent orcombination of rheology-modifying agents (such as water, a chemicaladmixture, or combination thereof) to the rheology, strength, or someother characteristic of the concrete that is modified by the effect ofthe rheology-modifying agent. The dose response curve may be representedin one of a number of forms, for clarity and convenience, and for easeof CPU programming. For instance, a dose response curve for a chemicaladmixture that modifies slump can be represented as the dose of chemicaladmixture as a function of the administered dose to the slump of theconcrete. Alternatively, it could be represented as the change inchemical admixture dose needed to change the slump by one incrementalunit (for example, admixture dose needed to change slump by one inch).

It is common to establish a dose response curve for a given set ofmaterials under a certain set of conditions, which can be later used toselect the proper dose during concrete production. This curve will bereferred to herein as the nominal dose response (“NDR”) curve. Becausethe dose response curve is a function of a large number of variables(material properties, temperature, etc.), it would be impracticallycomplex to develop dose response curves considering all relevantvariables, program a CPU with look-up tables or the like, measure allrelevant variables, and select the correct dose of therheology-modifying agent (e.g., chemical admixture) to achieve thedesired response. It is an object of this invention to provide a meansfor efficiently and accurately updating the nominal dose response curveto meet changing external variables, without the need to take thesevariables into account explicitly. Therefore, nominal dose responsecurves are generated and then adjusted by an adaptive controlmethodology.

The present invention arises from the surprising discovery that concretemixes having different parameters (e.g., temperature, mix design, waterlevels, hydration levels, humidity, different trucks) display “doseresponse” profiles that vary in amplitude but otherwise have similarbehavior in that their dosage response curves do not intersect. Theconcept of “dose response” as used herein shall mean and refer to theeffect of a particular rheology-modifying agent or combination ofrheology-modifying agents upon rheology (such as slump, slump flow, oryield stress) as a function of the administered dose.

This unexpected dose response behavior is illustrated in FIG. 1, whereinit is shown that different concrete mixes, into which arheology-modifying agent such as a polycarboxylate cement dispersantadmixture was admixed, show similar dose response curves wherein slumpis shown as a function of the dose amount (ounces of admixture per cubicyard of concrete) required to change slump by one unit (such as from 2to 3 inches slump, and from 3 to 4 inches slump, and so on). Thecalculation of a nominal dose response (“NDR”) profile is basicallyillustrated in FIG. 2, in which at least two profile curves (labeled“maximum dose” and “minimum dose” for convenient reference) areconsidered to provide one NDR profile.

The significance of the non-intersecting behavior of the dose responsecurves (FIG. 1) led the present inventors to the practical realizationthat one could adjust concrete rheology through use of an NDR profilebased on even one curve obtained form only one data set, although usingat least two curves is preferred (e.g., FIG. 2) and using a plurality ofcurves (e.g., FIG. 1) is more preferred from the standpoint of accuracy,the NDR profile can be adjusted by scaling only one parameter—namely, aratio reflecting the actual admixture performance and that predicted bythe nominal dose response curve. Thus, an adaptive control methodologyis achieved to update the nominal dose response curve based on actualadmixture performance. Each dose of admixture is selected by using thenominal dose response curve adjusted by the scaling factor from previousadditions of admixture into the same load of concrete. Thus, the dosesselected are adjusted to the actual conditions associated with theconcrete load without the need to measure and adjust explicitly forthese parameters. In such case, the second and each subsequent doses ofadmixture within a load are likely to be significantly more accuratethan the first dose. This eliminates a lengthy trial-and-error processwhere previous performance of admixture in the load of concrete is notconsidered.

It would be further possible to adjust the nominal dose response curvebased on admixture performance data from prior loads.

Although the prior art methods have suggested that empirical behavior ofthe concrete mix could be compensated for by use of water or chemicaladmixture, until now it has not been taught or suggested how thiscompensation was to be done. It is the surprising aspect of the presentinvention that the rheology of the concrete mix can be adjusted byinputting into a computer processor unit (CPU) only the amount of theconcrete (load size) and the target rheology value (e.g., slump, slumpflow, or yield stress), and comparing the actual rheology to the NDR,adding a percentage of the nominal dose the chemical admixture thatwould be (theoretically) required to change the actual rheology to thetarget rheology, measuring the resultant change in rheology value andcomparing this to the NDR value that would theoretically have beenobtained using the percentage nominal dose, and then adjusting therheology by adding a subsequent dose which takes into account thedeviation measured as a result of the first percentage addition. Hence,the present invention takes into account a “learning” step that isincorporated into the methodology, without having to consider numerousparameters such as temperature, mix design, humidity, and other factors.

Thus, an exemplary method of the present invention for controllingrheology of a hydratable cementitious composition in a mixer wherein theenergy required for operating said mixer containing the cementitiouscomposition is measured and correlated with a nominal rheology value andwherein a rheology-modifying agent is added into the cementitiouscomposition to modify its rheology comprises:

(a) entering into a computer processor unit (“CPU”) a target rheologyvalue (“TRV”) and load size for a hydratable cementitious compositioncontaining or intended to contain a particular rheology-modifying agentor combination of rheology-modifying agents; and

(b) obtaining a current rheology value (“CRV”) of hydratablecementitious composition contained within a mixer;

(c) comparing through use of CPU the current rheology value obtained instep (b) against a nominal dose response (“NDR”) profile stored inCPU-accessible memory and wherein said NDR is based on at least one dataset wherein various dose amounts of a particular rheology-modifyingagent or combination of rheology-modifying agents and their correlativeeffect on rheology value (such as slump, slump flow, or yield stress) isretrievably stored, and determining the nominal dose of said particularrheology-modifying agent or combination of rheology-modifying agentsrequired to change the obtained CRV to the TRV specified in step “(a)”;

(d) dosing the hydratable cementitious composition in a mixer with apercentage of said particular rheology-modifying agent or combination ofrheology-modifying agents that is selected or pre-selected from 5% to99% based on the nominal dose determined in step (c) required forchanging said obtained CRV to said TRV as specified in step (a);

(e) obtaining a subsequent CRV of the hydratable cementitiouscomposition after the percentage of the nominal dose of the particularrheology-modifying agent or combination of rheology-modifying agentsselected or preselected in step (d) is added into and uniformly mixedwith said hydratable cementitious composition; comparing the doseselected or preselected in step (d) to the dose according to the NDRprofile for the same change in the rheology value from step (b) to step(e), and determining the scaling factor (“SF”) by which to adjust thedose from the NDR profile, where SF is defined as the actual dose fromstep (d) divided by the nominal dose to achieve the same change inrheology value indicated by the NDR profile; and

(f) mixing into the hydratable cementitious composition the particularrheology-modifying agent or combination of rheology-modifying agents inan amount calculated in terms of SF multiplied by the dose from the NDRprofile indicated to convert the current CRV measured in step (e) to theTRV specified in step (a).

If the target rheology value such as slump is not attained uponcompletion of the aforementioned steps (which can be due to any numberof factors, such as temperature or humidity change), then process steps(e) and (f) can be repeated as required. In addition, concrete rheologychanges over time. Each time the rheology value decreases by a certainamount, a rheology-modifying agent (e.g., chemical admixture) must beadded to restore the rheology value. Steps (e) through (f) can berepeated to adjust the rheology value.

In preferred methods of the invention, the NDR profiles are calculatedbased on an average of at least two dose response curve values (seee.g., FIG. 2), and, more preferably, an average of a plurality doseresponse curve values obtained from trialing the particularrheology-modifying agent or combination of rheology-modifying agents(See e.g., FIG. 3).

In further exemplary embodiments, the system CPU can be programmed toassume a learning mode, whereby batch histories can be incorporated intothe NDR profile which is then stored into CPU-accessible memory, and/orthe scaling factor can be redefined so that dosing can be rendered moreaccurate. In other words, the rheology value changes effected by dosesof the rheology-modifying agent administered during a concrete mixdelivery operation are incorporated into the nominal dose response (NDR)curve or scaling factor whereby the NDR curve or scaling factor (SF) ismodified; and rheology value changes in a subsequent concrete mixdelivery operation or operations are effected based on the modified NDRcurve or modified SF.

Exemplary rheology modifying agents include water, a chemical admixture(e.g., polycarboxylate water reducer, naphthalene sulfonate formaldehydecondensate water reducer, melamine sulfonate formaldehyde condensatewater reducer, lignosulfonate water reducer, or hydrocolloid viscositymodifying admixtures such as welan gum or cellulose derivatives), ormixture thereof. Preferred are chemical admixtures such aspolycarboxylate cement dispersants, which are commonly used assuperplasticizers (or so-called high range water reducers) in theconcrete field. So long as the same rheology-modify agent or combinationof rheology-modifying agent is being used as was previously trialed forcreating the nominal dosage response (NDR) profile, then other variablessuch as concrete mix design, amount of water or cement or water/cementratio, aggregate selection or composition, degree of hydration, do notnecessarily need to be inputted into the CPU and remain optional.Viscosity modifying admixtures primarily affect the viscosity of theconcrete, while having a relatively lesser effect on other properties.

Further advantages and features of the invention may be describedhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and features of the present invention may be morereadily comprehended when the following detailed description ofpreferred embodiments is taken in conjunction with the appended drawingswherein

FIG. 1 is a graphic illustration of plurality of dose response curves(profiles) of various concrete mixes, whereby the effect of a particularrheology-modifying agent (e.g., chemical admixture such aspolycarboxylate water reducer) is measured upon the slump of theconcrete, as shown along the horizontal axis, is measured against thedose of the rheology-modifying agent whose amount, which is measured interms of ounces per cubic yard required to decrease the slump of theconcrete by one unit, as shown along the vertical axis;

FIG. 2 is another graphic illustration wherein at least two doseresponse curves (labeled minimum and maximum for the sake ofillustration) of a particular rheology-modifying agent are used tocalculate an average dose response profile, which may function as anominal dose response profile used in exemplary methods of the inventionfor automated control over concrete mix rheology; and

FIG. 3 is a graphic illustration wherein the theoretical (or nominal)slump change is plotted against the actual slump change when exemplarymethods of the invention are used.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The term “cementitious” as used herein refers to a material thatcomprises portland cement and/or portland cement substitutes that whenmixed with water function as a binder to hold together fine aggregates(e.g., sand), coarse aggregates (e.g., crushed stone or gravel), ormixtures thereof.

Cementitious materials considered to be “hydratable” or hydraulic arethose which harden by chemical interaction with water.

Such cementitious materials may further include fly ash, granulatedblast furnace slag, lime stone, or natural pozzolans, which may becombined with portland cement or be used to replace or substitute for aportion of the portland cement without seriously diminishing hydratableproperties. A “mortar” refers to cement or cementitious mixture having afine aggregate such as sand; while “concrete” refers more accurately toa mortar that also contains a coarse aggregate such as crushed stone orgravel.

The use of the term “cementitious material” may be used interchangeablywith the term “concrete,” as concrete is most commonly provided byready-mix trucks which have rotatable mixing drums. The term “concrete”as used herein does not necessarily exclude the fact that the presentinvention can be used for delivering materials that contain only cementor cement substitutes (e.g., pozzolans) or mortars.

Hydratable cementitious materials, such as concrete mixes, typicallycontain one or more rheology-modifying agents, which can include wateralone or chemical admixtures such as water-reducing agents or high rangewater-reducing agents called “superplasticizers,” viscosity modifyingagents, corrosion-inhibitors, shrinkage reducing admixtures, setaccelerators, set retarders, air entrainers, air detrainers, pigments,colorants, fibers for plastic shrinkage control or structuralreinforcement, and the like.

The phrase “rheology-modifying agent” will therefore be understood tomean and include water, a chemical admixture, or a mixture thereof. Inmany cases, a chemical admixture formulation will comprise a dispersantand water, for example. The rheology-modifying agent could well compriseone or more cement dispersants (e.g., polycarboxylate water reducer), anair detrainer or combination of detrainers, and other admixtures.

As mentioned in the background section, concrete delivery mixing truckshaving slump control monitoring and control equipment, such as hydraulicand/or electric sensors for measuring the energy for turning the mixingdrum, speed sensors for measuring the speed of rotation, temperaturesensors for monitoring the atmospheric temperature as well as the mixtemperature, and dispensing equipment, as well as the computerprocessing units (CPU) for monitoring signals from the sensors andactuating the dispensing equipment are by now relatively well known inthe industry. For example, such slump control systems, which can be usedin association with wireless communication systems, are disclosed inU.S. Pat. No. 5,713,663; U.S. Pat. No. 6,484,079; U.S. Ser. No.09/845,660 (Publication no. 2002/0015354A1); U.S. Ser. No. 10/599,130(Publication no. 2007/0185636A1); U.S. Ser. No. 11/764,832 (Publicationno. 2008/0316856); U.S. Ser. No. 11/834,002 (Publication no.2009/0037026); and WO 2009/126138. A further exemplary system formonitoring and control using wireless communications in combination withsensors for monitoring various physical properties of the concrete mixis taught in U.S. Pat. No. 6,611,755 of Coffee. These teachings, as wellas the patent references as previously discussed in the backgroundsection above, are expressly incorporated herein by reference.

Exemplary mixing drums contemplated for use in the present invention maybe ones that are customarily mounted for rotation on ready-mix deliverytrucks, as mentioned above, or on stationary mixers which may be foundin mixing plants. Such mixing drums may have an inner surface upon whichat least one mixing blade is attached to the inner surface so that itrotates along with the mixing drum and serves to mix the concrete mix,including the aggregates contained within the mix.

It is believed that a number of exemplary embodiments of the inventionmay be practiced using commercially available automated concrete mixmonitoring equipment with slight modifications as would be apparent inview of the invention disclosed herein. Such mix monitoring equipment isavailable under the VERIFI® name from Grace Construction Products,Cambridge, Mass., and also from RS Solutions LLC, West Chester, Ohio.

As previously described in the summary above, an exemplary method of theinvention for controlling rheology of a hydratable cementitiouscomposition in a mixer wherein the energy required for operating saidmixer containing the cementitious composition is measured and correlatedwith a nominal rheology value and wherein a particularrheology-modifying agent or combination of rheology-modifying agents areadded into the cementitious composition to modify its rheology,comprises the following steps:

(a) entering into a computer processor unit (“CPU”) a target rheologyvalue (“TRV”) and load size for a hydratable cementitious compositioncontaining or intended to contain a particular rheology-modifying agentor combination of rheology-modifying agents; and

(b) obtaining a current rheology value (“CRV”) of hydratablecementitious composition contained within a mixer;

(c) comparing through use of CPU the current rheology value obtained instep (b) against a nominal dose response (“NDR”) profile stored inCPU-accessible memory and wherein said NDR is based on at least one dataset wherein various dose amounts of a particular rheology-modifyingagent or combination of rheology-modifying agents and their correlativeeffect on rheology value (such as slump, slump flow, or yield stress) isretrievably stored, and determining the nominal dose of said particularrheology-modifying agent or combination of rheology-modifying agentsrequired to change the obtained CRV to the TRV specified in step “(a)”;

(d) dosing the hydratable cementitious composition in a mixer with apercentage of said particular rheology-modifying agent or combination ofrheology-modifying agents that is selected or pre-selected from 5% to99% based on the nominal dose determined in step (c) required forchanging said obtained CRV to said TRV as specified in step (a);

(e) obtaining a subsequent CRV of the hydratable cementitiouscomposition after the percentage of the nominal dose of the particularrheology-modifying agent or combination of rheology-modifying agentsselected or preselected in step (d) is added into and uniformly mixedwith said hydratable cementitious composition; comparing the doseselected or preselected in step (d) to the dose according to the NDRprofile for the same change in the rheology value from step (b) to step(e), and determining the scaling factor (“SF”) by which to adjust thedose from the NDR profile, where SF is defined as the actual dose fromstep (d) divided by the nominal dose to achieve the same change inrheology value indicated by the NDR profile; and

(f) mixing into the hydratable cementitious composition the particularrheology-modifying agent or combination of rheology-modifying agents inan amount calculated in terms of SF multiplied by the dose from the NDRprofile indicated to convert the current CRV measured in step (e) to theTRV specified in step (a).

As described in Step (a), the first step of the exemplary methodrequires inputting into a computer processor unit (“CPU”) only twopieces of information: the target rheology value (“TRV”) and the loadsize for the given hydratable cementitious composition that will beplaced into the mixer. The input of these two data points may beperformed by the batch master at the ready-mix plant, by the truckdriver, or foreman at the construction site. Indeed, this input may beperformed by anyone in charge of the concrete delivery and does notrequire the inputting of other parameters such as temperature, humidity,and other factors which are optional.

The target rheology value (TRV) may be any of the rheology factors whosemeasurement in unit values are customarily employed, such as: slump(customarily measured in terms of length units, e.g., inches); slumpflow (length, e.g., inches); yield stress (customarily measured in termsof stress, e.g., pounds per square inch or pascals); viscosity(pascals·seconds); flow (length); and thixotropy (pascals/second). Loadsize can be inputted into the CPU in terms of total weight or volume ofthe batch concrete (e.g., cubic yards) including all of the components.If the TRV is defined in terms of slump, then the measurement for slumpcan be done in accordance with the following standards: ASTM C 143-05,AASHTO T 119, or EN 12350-2. If the TRV is defined in terms of slumpflow, then this measurement can be done in accordance with ASTMC1611-05. If the TRV is defined in terms of the flow table test, thenthis can be done in accordance with DIN EN 12350-5.

The rheology-modifying agent or combination of rheology-modifying agentsmentioned in Step (a) means and refers to water, chemical admixture(s),or mixture thereof which are present in the concrete that is used forgenerating the data set or sets that provide the nominal dose response(“NDR”) profile mentioned in Step (c) as well as in the concrete beingadjusted, i.e., whose load size is inputted into the CPU in Step (a) andwhose current rheology value (CRV) is obtained in Step (b). It isimportant for purposes of calibration (i.e., generating the NDR profile)to use the identical or similar rheology-modifying agent(s) for the NDRprofile as for dosing into the concrete.

Preferred “chemical admixtures” suitable for use in methods of thepresent invention include water-reducers and superplasticizers commonlyused in the concrete industry. Preferred among these arecement-dispersing polymers which contain (poly)carboxylic acid and/orsalt groups and (poly)oxyalkylene groups (herein referred to as“polycarboxlate polymers”).

Thus, for example, the “rheology-modifying agent or combination ofrheology-modifying agents,” as this phrase is employed in Step (a), canrefer to one or more active ingredients, such as one or morepolycarboxylate polymers, which, in turn, may be used with airentrainers or other admixtures which may have an effect on the rheologyof the concrete. The concentration of the one or more active ingredientsis very important. One may need to establish and use another nominaldose response (NDR) profile if adding or omitting a particular activeingredient from the chemical admixture(s) formulation. The dispersingpolymers will be seen to affect rheology and will be deemed to be“active ingredients” such that it is preferable that the same polymersbe used in the NDR profile; this same reasoning applies for othercomponents such as air entraining and/or detraining components if bytheir amount and/or nature they will have a profound effect on therheology.

As one of the benefits of the present invention is that it isself-correcting, it may be possible to achieve high accuracy even wherethe cement-dispersing polymer is different and where other activeingredients might be different in nature and amount. However, when usingthe method of the present invention, it is preferable to start with thesame rheology-modifying agents or same combination of rheology-modifyingagents and to compensate for any differences in their concentrations.

In Step (b) of the exemplary method, this second step requires that thesystem determine the current rheology value (“CRV”) of the hydratablecementitious composition contained within the mixer. This is stored inCPU-accessible memory because it will provide a reference point forlater steps.

In Step (c) of the exemplary method, the CPU compares the currentrheology value (CRV) obtained in Step (b) with the nominal dose response(“NDR”) profile stored in CPU-accessible memory. As previouslymentioned, this NDR profile is based on at least one data set whereinthe effect of various dose amounts of a particular rheology-modifyingagent or agents on rheology (e.g., slump, slump flow, yield stress,etc.) is measured. While the method of the invention can work with onedata set wherein the effect of the rheology-modifying agent on rheologyis correlated, it is preferred to use an NDR profile that is generatedusing at least two data sets, and it is most preferably to use an NDRprofile that is generated using a plurality of data sets.

For example, FIG. 2 illustrates two dose response curves (labeledminimum and maximum) whereby the slump (inches) of a concretecomposition is plotted against the amount of the particularrheology-modifying agent (a slump-modifying concrete admixture) neededfor changing slump by one unit (e.g., for changing slump one inch, suchas from 2 inches to three inches). The nominal dose response profile (orcurve) then is taken as the average of the two dose response curves(minimum and maximum).

As a more preferred example, FIG. 1 illustrates a plurality of doseresponse curves whose average provides a nominal dose response (“NDR”)profile that may be used as a reference during a delivery operation.

In Step (d), the CPU is programmed to dose the hydratable cementitiouscomposition in the mixer using a selected or pre-selected percentage ofthe ideal amount of the rheology-modifying agent(s) that would bedetermined by the NDR profile to change the current rheology value(CRV), as determined in Step (b), to the target rheology value (TRV)entered in Step (a). The percentage may be 50% to 95% of the ideal (ornominal) amount, and more preferably would be about 50%-90%; and mostpreferably would be 50%-80%. Generally, the lower percentage in theseranges is preferable for this first dose until confidence is obtained.

In Step (e), the CPU would be programmed to obtain a subsequent currentrheology value (CRV) of the hydratable cementitious composition afterthe percentage of the nominal dose of the particular rheology-modifyingagent (e.g., chemical admixture) administered in Step (d) was added intoand uniformly mixed with the hydratable cementitious composition. TheCPU would compare the nominal (or theoretical) effect on the rheologyvalue of the percentage dose selected or preselected in step (d) to thesubsequent current rheology value (subsequent CRV) and then determinethe scaling factor (“SF”) by which to adjust the dose from the NDRprofile, where SF is defined as the actual dose from step (d) divided bythe nominal dose to achieve the same rheology change indicated by theNDR profile.

In Step (f), the CPU would be programmed to mix into the hydratablecementitious composition a subsequent dose of the rheology-modifyingagent. The amount of this subsequent dose would be calculated bymultiplying the scaling factor (SF) calculated in Step (e) by the amounttheoretically needed, according to the nominal dose response (NDR)profile, to change the subsequent current rheology value (CRV) measuredin Step (e) to the target rheology value (TRV) specified in Step (a).

Steps (e) and (f) may be repeated whenever the current rheology value(CRV) is less than or greater than the target rheology value (TRV) by apredetermined amount. This may be done automatically, for example, byprogramming the CPU to repeat this steps when the difference between theCRV and TRV exceeds a predetermined amount. If the difference betweenthe CRV and TRV is less than the predetermined amount, the CPU can beprogrammed to trigger an alarm to indicate to the operator that theconcrete mix is ready to be discharged and poured.

As mentioned above, preferred methods of the invention involve the useof a nominal dose response (NDR) profile which is derived from anaverage of at least two sets of dose response curves for the particularrheology-modifying agent(s), as illustrated in FIG. 2; and, morepreferably, from an average of a plurality of dose response curves forthe particular chemical admixture(s), as illustrated in FIG. 1. The doseresponse curves of FIG. 1 in particular suggests, by the varying curveamplitudes, that various parameters such as concrete mix design,temperature, degree of hydration, water/cement ratio, and aggregateamounts might be varying slightly (or even significantly) from batch tobatch. Still, the fact that the various dose response curves did notintersect led the present inventors to realize that these other variousparameters did not necessarily need to be kept constant in order toestablish a nominal dosage response (NDR) profile because the average ofthese dose response curves would have similar behavior in terms ofcalculating amounts of rheology-modifying agent(s) needed for changingthe rheology value (e.g., slump) from one value to the next (e.g., fromslump of 2 inches to, say, five inches).

Hence, exemplary methods of the invention involve a nominal doseresponse (NDR) profile involving the use of a plurality of data setshaving at least one non-homogeneous parameter. This parameter may, forexample, be the concrete mix design, temperature of reaction, degree ofcement hydration, the water/cement ratio, and the aggregate amount orcement/aggregate ratio. These may be varied from batch to batch in thedata sets which go to make up the NDR profile (See e.g., FIG. 1).

Thus, further exemplary methods of the invention comprise the use of anominal dose response (NDR) profile that is derived from data setshaving at least two non-homogeneous parameters, and even more than twonon-homogeneous parameters, such as different concrete mix design,concrete mix ingredient source, temperature, hydration, water/cementratios, different aggregate amounts or ratios, and concrete mix designs.So long as the particular rheology-modifying agent(s) (e.g., waterand/or concrete admixture or combination of chemical admixtures) usedfor setting up the NDR profile and for obtaining a current rheologyvalue is/are identical or substantially similar, the slope behavior ofthe dose response curves is similar from one rheology value unit to thenext. In fact, even if two rheology-modifying agents vary in compositionbut are similar in performance, it may be possible to use the same NDRprofile for both.

In further exemplary embodiments of the invention, the process ofmonitoring rheology change can involve the use of more than one type ofrheology-modifying agent (or chemical admixture) with each type ofrheology-modifying agent having its own scaling factor (SF), nominaldose response profile, or both. For example, one can establish NDRprofiles for combinations of chemical admixtures such as: high rangewater reducer with viscosity modifying admixture; normal range waterreducer with high range water reducer; water reducers with setaccelerators, set retarders, or combinations thereof; high range waterreducers with thixotropy modifying admixtures; and the like.

In still further exemplary embodiments, the method of the invention canbe modified so that more than one rheology target can be specified andmet within the same concrete mix delivery operation. For example, onemay use multiple rheology targets, such as slump target during transit(from batching or plant operation to job site) and during placement(after the truck arrives at the job site where the mix is to be poured).As another example, one may define two rheology targets that theconcrete mix must attain within the same delivery operation/process andat the same time, such as slump flow and plastic viscosity. It ispossible, in other words, to have one rheology-modifying agent orcombination of agents (e.g., admixture packages) for modifying the slumpflow (characterized by the spreading of concrete from a removed slumpcone) and to have another rheology-modifying agent or combination ofagents for modifying the plastic viscosity (characterized by shearstress divided by the shear rate).

In a further exemplary embodiment, the scaling factor is calculated as aweighted average of all dose responses in a given load or mix design. Inother words, in a series of delivery operations in which various scalingfactors are derived, the scaling factor used in the current deliveryoperation can be based on an average of all scaling factors computed,but primarily based on data obtained form the most recent deliveryoperations.

While the invention is described herein using a limited number ofembodiments, these specific embodiments are not intended to limit thescope of the invention as otherwise described and claimed herein.Modification and variations from the described embodiments exist. Morespecifically, the following example is given as a specific illustrationof an embodiment of the claimed invention. It should be understood, thatthe invention is not limited to the specific details set forth in theexample. All parts and percentages in the examples, as well as in theremainder of the specification, are by weight unless otherwisespecified.

Further, any range of numbers recited in the specification or claims,such as that representing a particular set of properties, units ofmeasure, conditions, physical states or percentages, is intended toliterally incorporate expressly herein by reference or otherwise, anynumber falling within such range, including any subset of numbers withinany range so recited. For example, whenever a numerical range with alower limit, RL, and an upper limit RU, is disclosed, any number Rfalling within the range is specifically disclosed. In particular, thefollowing numbers R within the range are specifically disclosed:R=RL+k*(RU−RL), where k is a variable ranging from 1% to 100% with a 1%increment, e.g., k is 1%, 2%, 3%, 4%, 5% . . . . 50%, 51%, 52%, . . .95%, 96%, 97%, 98%, 99%, or 100%. Moreover, any numerical rangerepresented by any two values of R, as calculated above, is alsospecifically disclosed.

Example 1

A concrete mixture was made in a laboratory mixer without any chemicaladmixtures added. Slump was measured by removing samples and placingthem in a slump cone in accordance with ASTM C143-05. When this test wasdone, the first mixture was discarded. Immediately thereafter, anotherconcrete mixture having the same concrete mix design was made in thesame laboratory mixer but this time with a chemical admixture(polycarboxylate water reducer), and slump was again measured using thesame standard cone test). When this test was done, the mixture wasdiscarded. A plurality of further successive concrete mixtures of thesame concrete mix design and identical mix factors (e.g., temperature,type of cement, amount of air and water, water/cement ratio, etc.) werealso made in the laboratory mixer, but each varying only in the dosageamount of the polycarboxylate polymer water reducer. Except for theadmixture dose of the water reducer, all other variables were keptconstant. Each successive mixture was discarded after slump conetesting.

The data for the above concrete mixes is illustrated as one plotted lineshown in FIG. 1.

The above process was repeated, but for each reiteration one of the mixfactors was varied while all other mix factors were kept constant. Thevaried mix factors included: temperature of the materials, the amountand type of cement, type of fine aggregate, type of coarse aggregate,amount of air in concrete, amount of water, and ratio of water tocement.

The data for these concrete mixes having a varied mix factor are alsoplotted as various lines shown in FIG. 1.

Surprisingly, the inventors discovered that the dosage response curves,as shown in FIG. 1, did not intersect. The present inventors thusdiscovered that the slump of the concrete mix could be adjusted byreference to the behavior of any curve or an average of all such dosageresponse curves, and that the behavior of such curve or plurality ofcurves could serve as a nominal or reference dosage response curveduring real time production-operation.

FIG. 2. is a simplified version of FIG. 1 showing “minimum,” “maximum,”and average dosage response curves. The average dose response curveshown in FIG. 2 can serve as a nominal dosage response curve during realtime production-operation.

Example 2

The exemplary method of the invention was tested in the field using aconcrete mix truck having an automated monitoring and dosing systemprovided by RS Solutions LLC of Ohio, commercially available under thetrade name VERIFI. This monitoring system could measure slump based onhydraulic pressure and mix drum speed. This system could also injectchemical admixture in liquid form into the mix drum from a smallchemical storage tank mounted on the fender. (Reference is also made toUS Patent Publication 2009/0037026, Sostaric et al., described in thebackground section).

Over a period of months a variety of concrete mixes were prepared in theconcrete mix truck. Prior to this testing, a nominal dose responseprofile was obtained, similar to the process described above in Example1, and this was used as the reference or “nominal” reference dose(“NDR”) profile.

A number of tests were run using the exemplary method of the inventionfor different concrete mix delivery operations, wherein the NDR was usedby the computer processing unit of the automated monitoring and dosingsystem for each successive concrete mix sample prepared in the mix drum.Mixes produced in the drum over the next few weeks experienced naturalvariations in terms of temperature, raw materials, mixture proportions(e.g., water/cement ratio, water/aggregate ratio, fine/coarse aggregateratio, etc.).

The amount of water reducing admixture (polycarboxlic acid-based) wasdosed in accordance with the method of the invention as described in theforegoing summary section.

As shown in FIG. 3, the use of the method resulted in slump changes inthe concrete mix that were very close to the predicted changes when thenominal dose response (NDR) curve was used as a reference. See methodsteps (a) through (f) in Summary section above. When the NDR curve isfirst applied, the slump change is then used to develop the scalingfactor (SF) which is then used on the next addition of admixture. FIG. 3illustrates that the actual measured slump change values (shown by thedots) closely match the theoretical slump change values.

The principles, preferred embodiments, and modes of operation of thepresent invention have been described in the foregoing specification.The invention which is intended to be protected herein, however, is notto be construed as limited to the particular forms disclosed, sincethese are to be regarded as illustrative rather than restrictive.Skilled artisans can make variations and changes without departing fromthe spirit of the invention.

1. A method for controlling rheology of a hydratable cementitiouscomposition in a mixer wherein the energy required for operating saidmixer containing the cementitious composition is measured and correlatedwith a nominal rheology value and wherein a rheology-modifying agent orcombination of rheology-modifying agents is added into the cementitiouscomposition to modify its rheology, wherein the improvement comprises:(a) entering into a computer processor unit (“CPU”) a target rheologyvalue (“TRV”) and load size for a hydratable cementitious compositioncontaining or intended to contain a particular rheology-modifying agentor combination of rheology-modifying agents; and (b) obtaining a currentrheology value (“CRV”) of hydratable cementitious composition containedwithin a mixer; (c) comparing through use of CPU the current rheologyvalue obtained in step (b) against a nominal dose response (“NDR”)profile stored in CPU-accessible memory and wherein said NDR is based onat least one data set wherein various dose amounts of a particularrheology-modifying agent or combination of rheology-modifying agents andtheir correlative effect on rheology value (such as slump, slump flow,or yield stress) is retrievably stored, and determining the nominal doseof said particular rheology-modifying agent or combination ofrheology-modifying agents required to change the obtained CRV to the TRVspecified in step “(a)”; (d) dosing the hydratable cementitiouscomposition in a mixer with a percentage of said particularrheology-modifying agent or combination of rheology-modifying agentsthat is selected or pre-selected from 5% to 99% based on the nominaldose determined in step (c) required for changing said obtained CRV tosaid TRV as specified in step (a); (e) obtaining a subsequent CRV of thehydratable cementitious composition after the percentage of the nominaldose of the particular rheology-modifying agent or combination ofrheology-modifying agents selected or preselected in step (d) is addedinto and uniformly mixed with said hydratable cementitious composition;comparing the dose selected or preselected in step (d) to the doseaccording to the NDR profile for the same change in the rheology valuefrom step (b) to step (e), and determining the scaling factor (“SF”) bywhich to adjust the dose from the NDR profile, where SF is defined asthe actual dose from step (d) divided by the nominal dose to achieve thesame change in rheology value indicated by the NDR profile; and (f)mixing into the hydratable cementitious composition the particularrheology-modifying agent or combination of rheology-modifying agents inan amount calculated in terms of SF multiplied by the dose from the NDRprofile indicated to convert the current CRV measured in step (e) to theTRV specified in step (a).
 2. The method of claim 1 wherein steps (e)and (f) are repeated whenever the CRV is less than or greater than theTRV by a predetermined amount.
 3. The method of claim 1 wherein said NDRprofile described in step (c) is derived as an average of at least twosets of dose response curves for the particular rheology-modifying agentor combination of rheology-modifying agents.
 4. The method of claim 1wherein said NDR profile described in step (c) is derived as an averageof a plurality of dose response curves for the particularrheology-modifying agent or combination of rheology-modifying agents. 5.The method of claim 4 wherein, in said NDR profile, at least two doseresponse curves contains at least one non-homogeneous parameter selectedfrom concrete mix design, concrete mix ingredient source, temperature,degree of hydration, water/cement ratio, and aggregate amount.
 6. Themethod of claim 5 wherein, in said NDR profile, at least two doseresponse curves contains at least two non-homogeneous parametersselected from concrete mix design, concrete mix ingredient source,temperature, degree of hydration, water/cement ratio, and aggregateamount.
 7. The method of claim 4 wherein the particularrheology-modifying agent or combination of rheology-modifying agentscomprises water, at least one cement dispersant, or mixture thereof. 8.The method of claim 7 wherein said at least one rheology-modifying agentis a cement dispersant.
 9. The method of claim 8 wherein said cementdispersant is a lignosulfonate, naphthalene sulfonate, melaminesulfonate, polycarboxylate, or mixture thereof.
 10. The method of claim8 wherein said cement dispersant is a polycarboxylate polymer.
 11. Themethod of claim 1 wherein said mixer is a rotatable mixing drum mountedon a ready-mix delivery vehicle.
 12. The method of claim 1 wherein saidrheology value is slump which is correlated with the slump of a standard12-inch slump cone.
 13. The method of claim 1 wherein said rheologyvalue is slump flow.
 14. The method of claim 1 wherein said rheologyvalue is yield stress.
 15. The method of claim 1 wherein said rheologyvalue is thixotropy.
 16. The method of claim 1 wherein said rheologyvalue is plastic viscosity.
 17. The method of claim 1 wherein saidrheology value is flow table spread.
 18. The method of claim 1 whereinrheology value changes effected by doses administered during a concretemix delivery operation are incorporated into said nominal dose response(NDR) curve or scaling factor whereby said NDR curve or scaling factor(SF) is modified; and subsequent rheology value changes in the same or asubsequent concrete mix delivery operation are effected based on saidmodified NDR curve or said modified SF.